Flat-panel display devices have numerous advantages of thin body, power saving, no radiation and so on, and thus are widely applied. The current flat-panel display devices mainly include liquid crystal display (LCD) devices, and organic light emitting display (OLED) devices. A thin film transistor (TFT) is a significant component of a flat-panel display device, may be formed on a glass substrate or a plastic substrate, and is generally applied to the LCD, OLED and the like as a light emitting device and a driving device.
Polycrystalline silicon (poly-Si) thin film is formed of a large amount of small grains with different sizes and different crystal orientations, wherein a grain size generally ranges from tens to hundreds of nanometers, and a large grain size may reach several microns. The poly-Si thin film formed of large grains has higher migration rate that is approximate to a migration rate of bulk materials. Thus, the poly-Si thin film has been widely applied to the manufacturing of semiconductor devices. For example, the TFTs in the products of LCD or OLED mostly adopt the poly-Si thin film as an active layer.
Currently, a method of manufacturing the poly-Si thin film mainly firstly prepares amorphous silicon (a-Si) thin film, and then performs a crystallization process on the a-Si film to obtain the poly-Si thin film. The crystallization process performed on the a-Si thin film mainly includes excimer laser anneal (ELA), metal induced crystallized (MIC), metal induced lateral crystallization (MILC), solid-phase crystallization (SPC) and so on. If the poly-Si is manufactured using the ELA, the poly-Si has low defect state density, and it is difficult to manufacture a large area of the poly-Si thin film; in addition, the device used by this method is expensive, and the cost is high. In the poly-Si thin films manufactured using the MIC and MILC, there is much metal residual, so that characteristics of the TFT become worse. The poly-Si thin film having the larger grain size may be manufactured using the SPC. However, if this method is applied to manufacturing the TFT array substrate, since a base substrate is easily deformed at high temperature, it needs to set a temperature of the crystallization lower, and the reduction of the crystallization temperature causes crystallization time to be greatly increased, thereby reducing production efficiency.